1. Field of the Invention
The present invention relates to a magnetic thin film with superior high-frequency characteristics in a GHz band and a method of forming the magnetic thin film, a magnetic device and an inductor including such a magnetic thin film, and a method of manufacturing a magnetic device.
2. Description of the Related Art
In recent years, as an integrated passive component, a planar magnetic device such as a thin film inductor or a thin film transformer is desired to be used at a high frequency, and a magnetic thin film with superior high-frequency characteristics in a GHz band is desired accordingly.
Suggestions for improving the high-frequency characteristics of the magnetic thin film include increasing a resonant frequency, preventing a high-frequency current loss and so on. Among them, in order to increase the resonant frequency of the magnetic thin film, it is necessary to increase the values of an anisotropic magnetic field Hk and saturation magnetization 4π Ms on the basis of the following formula (1).
[Mathematical Formula 1]
            f      r        =                  γ                  2          ⁢          π                    ⁢                        4          ⁢          π          ⁢                                          ⁢                                    H              K                        ·                          M              S                                                (                                                    ⁢                                          f                r                            ⁢                              :                            ⁢                                                          ⁢              resonant              ⁢                                                          ⁢              frequency                                                                                    ⁢                          γ              ⁢                              :                            ⁢                                                          ⁢              gyromagnetic              ⁢                                                          ⁢              constant                                                                                    ⁢                                          H                k                            ⁢                              :                            ⁢                                                          ⁢              anisotropic              ⁢                                                          ⁢              magnetic              ⁢                                                          ⁢              field                                                                                    ⁢                                          M                S                            ⁢                              :                            ⁢                                                          ⁢              saturation              ⁢                                                          ⁢              magnetization                                            )  
As a technique for providing the anisotropic magnetic field Hk for the magnetic thin film, a technique of treating the magnetic thin film with heat in a magnetic field (for example, refer to Japanese Unexamined Patent Application Publication No. H5-114530) is conventionally used, and a technique of forming a magnetic layer in a magnetic field (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-20864) is also used recently.
Moreover, when such a magnetic thin film is actually applied to a magnetic device, it is important that the value of the anisotropic magnetic field Hk is not only large but also freely controllable according to purposes of use or applications.
For example, in S. Ohnuma et al. “Magnetostriction and soft magnetic properties of (Co1-xFex)—Al—O granular films with high electrical resistivity”, Journal of Applied Physics, American Institute of Physics, Apr. 15, 1999, Vol. 85, No. 8, p. 4574-4576, a technique of controlling the anisotropic magnetic field Hk through changing the composition of cobalt (Co) and iron (Fe) in a (Co1-xFex)—Al—O magnetic film is disclosed.